Known in the art are a whole number of radical-polymerization initiators. These may be exemplified by aliphatic azo compounds of the formula: ##STR3## which are produced by way of chlorination of azines of the ketones with molecular chlorine in the medium of acetic acid (cf. S. Goldschmidt, B. Akchsteiner, J. Liebigs Ann.Chem., 1958, 61, 8 s. 173-185; W. Bracke, J. A. Empen, C. S. Marvel, Macromolecules, 1968, 1161, p. 465-468).
Furthermore, as radical-polymerization initiators use is made of symmetric aliphatic compounds of the formula: X(CH.sub.2).sub.n CR.sub.1 R.sub.2 N.dbd.NCR.sub.1 R.sub.2 (CH.sub.2).sub.n X,
wherein X is Cl or Br, R.sub.1 and R.sub.2 are each a C.sub.1 -C.sub.20 alkyl, n=0 to 5 (cf. FRG Pat. No. 2,546,377 Cl. C 08 F 295/00).
These compounds when used as initiators for radical polymerization of ethylenically unsaturated monomers have a high thermal stability which hinders and frequently even precludes their application, in particular in the manufacture of reactive telechelate oligomers.
Furthermore, the above-specified compounds contain primary chloroalkyl groups possessing but a low reactivity in reactions of copolycondensation or copolyquaternization (cf. E. N. Barantzevich, N. K. Beresneva, A. E. Kalaus, T. S. Saburova "Kauchuk i Rezina", 1976, No. 9, p. 7-9; "General Practicum in Organic Chemistry", MIR Publishing House, M., 1965, p. 318; B. N. Pronin, E. N. Barantzevich, S. S. Ivanchev "Vysokomolekularnyje Soedinenija", 1977, 19(3), 455-458).
It is also known, as a radical-polymerization initiator, 2-(tert.butylazo)-2-acetoxy-4-methyl-4-(tert.butyl-peroxy)-pentane of the formula: ##STR4## (cf. U.S. Pat. No. 4,088,642; Cl. 260/174, Int. Cl. C 07 c 107/02).
This compound, due to its asymmetry, provides, during decomposition, radicals having different chemical structure, wherefore its use as an initiator for the manufacture of telechelate oligomers with identical functional groups is impossible.
Furthermore, known as radical-polymerization initiators are .alpha.,.omega.-bis-alkyl esters derivatives of .alpha.,.alpha.'-azo-bis-isobutyric acid of the formula: ##STR5## wherein R is CH.sub.2 CH.sub.2 Cl, --(CH.sub.2 CH.sub.2 O).sub.n OH.
These compounds are prepared by treating .alpha.,.alpha.'-azo-bis-isobutyric acid dinitrile and ethylene chlorohydrin or ethylene glycol or polyethylene glycol with hydrogen chloride in an organic solvent medium, followed by treating the resulting reaction mixture with water and isolation of the desired product by distilling-off the solvent from the desired product, extraction or recrystallization of the desired product. (Cf. FRG Offenlegungschrift No. 2,124,000 Cl. C07 C 107/02).
These compounds contain, as reactive functional groups, only OCH.sub.2 CH.sub.2 Cl or --OCH.sub.2 CH.sub.2 OH, whereby the field of their application in chemical reactions is limited, especially in such reactions as radical polymerization, polyquaternization, polycondensation.
The novel compounds according to the present invention, i.e. .alpha.,.omega.-bis-alkyl-ester derivatives of .alpha.,.alpha.'-azo-bis-isobutyric acid are hitherto unknown from the literature.